Conversational videotelephony services have recently experienced strong growth. Such services consist of the combined use of video, audio, and text to hold a conference involving multiple participants.
In addition to traditional audio/video conferencing methods, a discussion functionality (“chat”) is necessary for exchanging messages in the form of text data. In a point to point exchange between two participants, there are processes for sending text back and forth independently of the video exchange, for example entering text the client side and sending it off when sentences are completed.
An example of such a point to point system is illustrated in FIG. 1A. In this conventional system, the terminals A and B exchange video data over a first exchange channel 1, audio data over a second exchange channel 2, and text data over a third exchange channel 3. The transfer of text data is controlled by a text communication protocol, such as the T.140, SIP Message, or SIP Info protocols.
A first problem arises if conducting text conversations between two terminals using different text communication protocols or protocols that are incompatible. This problem is illustrated in FIG. 1B. In this figure, in addition to the usual exchange channels video 1 and audio 2, terminal A for example uses a text data exchange channel 4 managed by a T.140 protocol, while terminal B uses a text data exchange channel 5 managed by a SIP Message protocol. In such a case, terminal B cannot receive the text data on channel 4, and conversely terminal A cannot receive the data on channel 5.
This problem is particularly acute in multipoint videoconferencing systems, where a central control unit manages the videoconference between multiple participants, typically more than three.
This is illustrated in FIG. 1C. In this figure, in addition to the usual video 1 and audio 2 exchange channels, terminal A uses a text data exchange channel 6 managed by a T.140 protocol. It receives text data from a terminal B on a text data exchange channel 7 managed by the same T.140 protocol, as well as text data from a terminal C on a text data exchange channel 8 managed by the SIP Message protocol. In such a case, the terminal A can communicate textually with terminal B, but is unable to communicate textually with terminal C.
One can see from FIG. 1C that the more participants there are in a multipoint videoconference, the greater the chances of having a problem in exchanging text data, because if any participant uses a different text communication protocol or an incompatible protocol, the text conversation will fail.
In addition, there is no uniformity in the presentation of the text conversation in such a context, and it will depend on the possibilities of each terminal.
Of course, one solution to this problem with holding text conversations during a videoconference between multiple participants, is of course to require each participant to use the same text communication protocol, such as the terminals A and B in FIG. 1C. However, this is an unwieldy constraint to implement, and is sometimes impossible when the terminals of the participants already have their own text communication protocol that cannot be changed. In addition, the terminals of the participants don't know how to receive text data originating from multiple text sources, even if they use the same protocol. Thus most terminals do not support the multipoint text dialog function.